From the O's Mailbag column on Orioles.com, Spencer addresses a question of having Millar hit in the No. 2 spot:
Millar is in fact one of the team's most patient hitters, but he's also a
fairly slow runner who clogs the bases.
The old "clogs up the bases" argument. You can't score if you don't get on
base. Millar gets on base. I don't care if he clogs them up or not as long
as he's on base. Silly argument.
Mora's also pretty patient, but he runs well, hits for power and is willing to drop down a bunt in a key spot.
This is a better argument, that Mora fits the classic No. 2 hitter mold better than Millar. But hitting for power? Millar slugged .437 while Mora slugged an anemic .391. I'm also not sure giving up an out in the form of "moving a runner over" is the best tactic with Markakis, Tejada and Huff waiting on deck (save for late game situations obviously).
The last time the first baseman hit 20 home runs was 2003, and the last time he slugged over .500 was 2002. Millar is a patient hitter with a moderate amount of power, but the O's are very comfortable with him at the bottom of the order.
I'm not sure what this really has to do with hitting in the 2 spot but Millar hit 15 homers, only one less than Mora while getting almost 200 fewer at-bats. On pure power, Millar would win the day.
I wouldn't put Millar in the 2 spot full time (I wouldn't put him anywhere full-time) but batting him second isn't the craziest idea I've ever heard.